Plants α-diversity and biomass have a significant impact on global climate and environmental changes. The fluctuation of temperature and precipitation caused by climate change is a driving force for the dynamic change of plants α-diversity and biomass. Therefore, our study was conducted in the desert grassland of Ningxia, China (E 107.285, N 37.763), and involved an experiment with five levels of annual precipitation (33% [R33], 66% [R66], 100% [CK], 133% [R133], and 166% [R166]) and two temperature levels (inside and outside the open-top chamber [OTC]). Our objective was to determine how plants α-diversity in desert grasslands respond to changes in precipitation and warming. Our study suggests that aboveground living biomass (ALB) and root biomass (RB) of plants increased with precipitation increasing. Plants diversity, richness and evenness were improved from 0.1 to 0.2 under warming. TR33, TR66, TRCK, TR133, and TR166 all decreased plants α-diversity under the interaction of precipitation and warming, with TR33 and TR66 having a stronger effect on the correlation between community α-diversity indices than the other treatments. TR133 and TR166 increased ALB by nearly 20g/m² but decreased RB by nearly 15g/m². Our findings provide a reliable theoretical basis for the formulation of reasonable response strategies for desert steppe ecosystems.